Chemical structure, biological sequence, and large molecule rendering software is widely used by research and educational institutions to depict chemical structures, chemical reactions, and biological sequences (including nucleotide and amino acid sequences) of interest. Unlike chemical formulas or chemical names, chemical structure formulas provide a graphical representation of the molecular structure. A graphical chemical structure representation is capable of indicating the arrangements of atoms in a way that a chemical formula cannot. Similarly, large molecules and other biological sequences can be graphically represented in various ways; for example, a biological sequence can be represented textually by a sequence of letters corresponding to nucleotide codes or amino acid codes. Alternatively, a two- or three-dimensional graphical representation may be determined from a nucleotide and/or amino acid sequence to depict the arrangements of atoms, nucleotides, and/or amino acid residues of the biological molecule as a chemical structure, a ball-and-stick model, a ribbon diagram, a space-filling model, or an electrostatic model.
Current methods for drawing and editing biological and chemical structures on a computer utilize mouse-driven or touch pad commands that include pointing and clicking on displayed menu items in a graphical user interface. Existing chemical and biological structure rendering applications for handheld electronic devices such as tablet computers and portable phones utilize the same menu-driven paradigm. These applications can be clumsy and difficult to use for drawing purposes. For example, it may be difficult to identify connections made between elements within a chemical or biological structure drawing because the drag and drop touch screen interface becomes obscured by the hand during gesture-based manipulation of drawing elements.